Five-Body Integral Equations and Solution of the η-4N Problem

The Alt–Grassberger–Sandhas equations for the five-body problem are solved for the case of the driving two-body potentials limited to s-waves. The separable pole expansion method is employed to convert the equations into the effective quasi-two-body form. Numerical results are presented for five identical bosons as well as for the system containing an η-meson and four nucleons. Accuracy of the separable expansion is investigated. It is shown that both in (1 + 4 ) and (2 + 3 ) fragmentation, the corresponding eigenvalues decrease rather rapidly, what, combined with the alternation of their signs, leads to rather good convergence of the results. For the η- 4 N system the crucial influence of the subthreshold behavior of the ηN amplitude on the η-nuclear low-energy interaction is discussed.